The regeneration of chemical-spent acid from industrial processes is highly desirable for a verity of reasons, ranging from reducing industrial waste and contamination of landfills to reduction of costs associated with the reproduction of acid.
The recovery of acid has been demonstrated in a variety of industrial set-ups.
U.S. Pat. No. 2,631,974 [1] discloses an electrolytic system for the recovery of certain ingredients from the waste liquors discharged from various chemical processes, in particular with the recovery of sulfate ions in acid aqueous solutions containing them by the conversion thereof into aqueous sulfuric acid solutions of sufficient purity to be of commercial value.
U.S. Pat. No. 8,052,953 [2] discloses a method for recovering sulfuric acid from concentrated acid hydrolysate of plant cellulose material.
One of the main barriers in utilizing acid in industrial applications is the relatively high cost which is associated mainly with a high energy requirement needed to recover it. Therefore, there is great need for reducing the production cost and energy requirements involved in such processes.
Sulfuric acid is one of the more common acids in industrial use. The addition of hydrogen peroxide to sulfuric acid results in the formation of a very strong oxidizer, known as Caro's Acid or the Piranha solution, which has the ability to oxidize or hydroxylate most metal surfaces and remove most organic matter. The common application of the Piranha solution is in the microelectronics industry to clean photoresist residues from silicon wafers. It is also used to clean glassware by hydroxylating the surface, thus increasing the number of silanol groups on the surface.
U.S. Pat. No. 3,856,673 [3] discloses a process for purifying a spent acid stream containing organic impurities and at least 60% sulfuric acid. The process disclosed utilizes a stoichiometric amount of an oxidizer such as hydrogen peroxide to achieve oxidation of organic materials such as nitrocresols and nitrophenolic compounds.
Huling et al [4] teach oxidation of organic compounds utilizing hydrogen peroxide.